The head of the North Korean army has been relieved of all his duties, with state media citing "illness" as the reason for his departure.

Analysts believe Ri Yong-ho has been replaced because he was becoming too powerful and that his sudden fall from power sends a “strong signal” to others that the regime will tolerate no rivals to Kim Jong-un.

It also coincides with other moves to reinforce Kim’s control over the state.

His older half-brother, Kim Jong-nam, has been ordered by senior government officials to say nothing that could be construed as being critical of the regime, particularly on the question of hereditary succession in a communist state.

Kim Jong-nam was once considered the likely heir to the regime but infuriated his father, Kim Jong-il, when he was arrested in 2001 trying to enter Japan on a fake Dominican Republic passport. He told investigators that he wanted to visit Disneyland.

Exiled to Macau, he has in recent years been outspoken about the North Korean regime, but has now apparently been warned off.

A second strategy that Pyongyang has apparently set in motion is the introduction of an unnamed woman attending public events alongside Kim Jong-un.

On Saturday the mystery woman was shown on state television visiting a kindergarten in the North Korean capital with Kim. This is the third time that the attractive, short-haired woman has been shown with Kim and sources in the South Korean government told Yonhap news that the woman is “highly likely” to be his wife.

The introduction of the “Young General’s” partner is seen as an effort to play down any concerns at home that Kim—at 29 the youngest national leader in the world—is too immature and inexperienced to lead a nuclear-armed state.

As well as making him appear more grown-up, having an attractive young wife would give Kim more charisma, experts believe.

The firing of Ri, however, appears to have caught intelligence agencies by surprise.

Ri was promoted to chief of the General Staff of the Korean People’s Army in 2009 and was seen as a close confidant of Kim, who became the leader of the reclusive state at the age of 28 when his father died suddenly in December.

Ri walked alongside the black limousine of Kim Jong-il’s funeral cortege and was regarded by analysts as acting as a mentor to the young and inexperienced leader.

In recent weeks, he had been pictured on state television accompanying Kim Jong-un on inspection tours of military facilities across North Korea and his position appeared to be secure.

On Monday, the official KCNA news agency announced that a meeting of senior officials from the ruling party had been convened the previous day and it was decided that Ri should be relived of all his positions.

“A meeting of the political bureau of the central committee of the workers’ party decided to relieve Ri Yong-ho of all his posts for his illness,” the report said.

Ri will also no longer serve as vice-chairman of the central military commission of the Workers’ Party of Korea, it added.

But Daniel Pinkston, senior analyst at the International Crisis Group, told The Daily Telegraph from Seoul that Ri’s fate may have been sealed as far back as April, when the fourth Party Conference failed to confer any promotions on him while others received a range of new titles.

“Being passed over like that indicates he was being reigned in,” he said.

Ri previously paid a state visit to Cuba during which he made bombastic statements that North Korea would fight alongside Cuban troops to defeat the American “imperialists” and there was apparently concern back in Pyongyang that he was overstepping his bounds.

“A dictator has to put mechanisms in place to prevent coups and challenges to his power,” said Pinkston. “This will not only have been aimed at this individual but it will also serve as a signal to others.”

An alternative suggestion is that Ri may have actively been plotting against Kim’s fledgling regime, although that is difficult to prove from outside the borders of the reclusive state.

“In these sort of dictatorships, purges are used as a policy instrument and designed to send the chilling message that the regime is willing to take action,” said Pinkston. “And that is even more chilling when the person is one of the most senior members of the inner circle.”

If Ri does not resist his demotion, he is likely to be able to take an “honourable retirement,” but if he opposes the decision he is likely to be imprisoned in North Korea’s infamous gulag system.

“And if he was actively plotting against Kim, then he and his family will face serious retribution,” Pinkston said.

Ri’s fall from grace sends the signal that Kim is “in full control” in Pyongyang, he added, and that no one is in a position to challenge his authority.